2. Blood Bank Genetics

Question 1

Who is the “Father of Modern Genetics”?

Answer 1

Gregor Mendel

• Discovered “elementens” = genes
• Genes are passed along to next generation independently

Question 2

Dominance: Genotype vs. Phenotype

Answer 2

Genotype: Genetic makeup
Phenotype: Observed expression of genes
e.g. T = dominant; t = recessive

Question 3

Locus & Allele: Definition

Answer 3

Locus: Chromosomes possess genes at specific location
Allele: Alternative forms of a gene at each specific locus

Question 4

RBC Gene Inheritance

Answer 4

• RBC genes determine antigens present
• RBC genes and antigens are co-dominant
• If the antigen is present, it is expressed

Question 5

RBC Gene Inheritance: What is an amorphic gene?

Answer 5

“Silent Gene”: does not produce detectable antigen

e.g. “O” gene is amorphic - no “O” antigen

Question 6

How can we predict inheritance?

Answer 6

Utilizing punnett squares

Question 7

Homozygous vs. Heterozygous

Answer 7

Homozygous: Double expression of one allele
e.g. EE, ee, MM, NN
Heterozygous: Non-identical pairs
e.g. Ee, MN

Question 8

Paternity Confirmation: Inheritance of Alleles

Answer 8

• Humans inherit one chromosome with allelic form from each parent
• Linkage between some blood groups/antigens
  e. g. NS will move as unit, Ms will move as unit

Question 9

Previously used in Paternity Testing: Direct Exclusion

Answer 9

Direct exclusion of alleged father: Child has “marker” that is absent from mother and alleged father or Father has two markers, child has neither

Question 10

Previously used in Paternity Testing: Indirect Exclusion

Answer 10

Indirect exclusion of alleged father: Child has single “marker” (homozygous) or Father has different single “marker” (homozygous)

Question 11

Ag/AB Dosage Effect: What is the significance of homozygous ag expression?

Answer 11

Homozygous ag expression can result in stronger reactions with corresponding ab compared with heterozygous ag expression

Question 12

Dosage: 2 options

Answer 12

1) Stronger against homozygous, weaker against heterozygous

2) Dosage reacts with homozygous only

Question 13

Phenotype Frequency in Population: Hardy-Weinberg Effect

Answer 13

Genotypes are distributed in proportion to the gene frequencies and will remain constant from generation to generation
** Application + Calculation

Question 14

William Walter has a history of anti-e and anti-K and needs 2 RBCs for transfusion. How many RBCs must be screened to find 2 compatible RBCs to transfuse. Given: e frequency is 98%, K frequency is 9%.

Answer 14

110 RBCs